Looking for old advertisements? One great place is in the NY Times Historical. It's the NY Times, including display ads as well as articles, 1851-2004!
Click on Articles/Databases, then "N" in the a-z list, then click on NY Times Historical. Change the "document type" drop down to "display ads," put in the date range you want, and search for ads. Displayed here is an ad from 1950 using the word "diaper" for a search.